The present invention relates to multilayer film structures having improved seal and tear properties. Specifically, the film structures of the present invention can be used alone or laminated to another film or a packaging film component thus forming a package, which contains a product. The film structures of the present invention are particularly useful for packaging of flowable materials including but not limited to condiment packaging.
Packages for enclosing products are usually made by forming a polymeric film into a shape to accommodate the product, placing another polymeric film over the product and then heat sealing the film together to maintain the product within the two film structures. Packages for products may also be made by forming a polymeric film into a pouch, heat sealing closed all but one of the open edges, filling the pouch with a product, and then heat sealing closed the one open edge. Both of these generally described processes for making packages are known in the art. The packages made from the above-described processes can have problems in their heat sealing properties and if the package is intended to be opened by a consumer, in their tear properties. These problems are especially acute if the package, which contains a flowable material, is intended to be opened by a consumer wherein a combination of good seal and good tear properties are necessary.
In forming heat seals in packages, especially packages for flowable materials, two films (i.e., a film and another film or two portions of the same film) are brought together, and then sufficient heat and pressure are applied to fuse or seal the films together. Colorants are added to packaging film structures to provide a more aesthetically pleasing package or to provide a background for printed material. If the film is a multilayer film, then the colorant is blended with one or more layers of the film, and specifically the colorant is blended with a polymeric material which comprises a layer or layers of the film structures.
Packages, especially packages for the containment of flowable materials, need good seal properties and good tear properties. Good seal properties are necessary to insure that the flowable material does not leak from the package. Good tear properties are necessary to insure that the package can be opened easily by the consumer without tearing through the entire package causing spillage of the flowable material.
U.S. Pat. No. 5,879,768 and U.S. Pat. No. 5,360,648 both to Falla, et al. disclose pouches for packaging flowable materials. In particular, a pouch made from a monolayer or multilayer film structure such as a two-layer or a three-layer coextruded film is disclosed. The film structure contains at least one layer of a blend of a substantially linear ethylene polymer or a homogeneously branched ethylene polymer and a high pressure low density polyethylene as a seal layer. In addition, the film structure contains a pigment to render the film structure opaque.
U.S. Pat. No. 5,360,648 to Rivett et al. discloses a heat-sealable, multilayer film containing a colorant and method for making a package with such film. In particular, the multilayer film includes:                a. a first layer comprising a material having a melting point of at least 145° C.;        b. a second layer comprising a colorant blended with a polymer having a vicat softening point ranging from 100° C. to 140° C.;        c. a third layer comprising a material having a melting point of at least 135° C.; and        d. a fourth layer comprising a material which is capable of forming a heat-seal,        wherein the second layer is positioned between the first and third layers and the fourth layer is an exterior layer.        
The art has not provided packages for flowable materials having the unique combination of both good seal and good tear properties. The prior art packages appear to be lacking in that packages with good seal properties have not had good tear properties, and packages with good tear properties have not had good seal properties. Accordingly, there is a need in the art of flowable material packaging for a package which has good seal and good tear properties, can be produced in a cost-efficient manner and is easy to process.